Light curtains have a number of applications, such as to perform a variety of measurement and inspection functions. Light curtains are used to size parts, verify part features such as edges, holes and other distinguishing characteristics, and for verification of part ejection. Light curtains may also be used on many types of industrial machinery, such as punches, presses, drills, saws, etc., in order to sense the presence of foreign objects or as part of security or safety systems.
Light curtain devices typically employ a number of light beams that are disposed to fan out across a designated location in a production line. Typically, such devices employ a plurality of active elements on both sides of the area to be monitored. For example, a plurality of light generators, each of which generates a light beam or column, may be disposed on one side of the monitored area, and a corresponding plurality of light detectors may be disposed on the other side of the monitored area. The interruption of one or more of the light columns thus indicates, for example, the presence of a part at the monitored area, and tracking of which light columns are interrupted can be used, for example, to determine the type or orientation of the part at the monitored location.
Therefore, the alignment of the light curtain is important. However, use of the light curtain over an extended period of time or in a warm factory setting can place thermal stress on one or more of the components of the light curtain potentially affecting the disposition of the components of or within the light curtain relative to one another. This may further affect the alignment of the light curtains resulting in additional alignment procedures, or a decrease in range of the light curtain.
Accordingly, what is needed is a light curtain with improved alignment that is consistent over time and throughout changes in the environment in which it operates.